A wheel having a uniform distribution of mass will spin evenly and can be referred to as balanced. If the mass is not evenly distributed, the wheel will tend to vibrate and/or wobble at high rates of rotation. Many wheels, including aircraft wheels, have mass variations caused by the manufacturing process, or by valves or other elements on the wheel that make the distribution of mass on the wheel asymmetric. Wheels are therefore often balanced by adding small weights thereto to compensate for such asymmetries.
Aircraft wheels may include inflation and safety relief valves that tend to make the distribution of weight uneven. Thus, weights may be added to these wheels during the balancing process to counterbalance the mass of the valves. A tire pressure indicator system (TPIS) may also be added to an aircraft wheel after it is balanced. To offset the mass of the TPIS, counterweights are often provided with the TPIS that can be installed opposite the TPIS to substantially maintain wheel balance. Thus a wheel with an inflation valve, a safety valve, a TPIS and a TPIS counterweight is relatively evenly balanced.
A hubcap may be installed on the wheel after balancing. The mass distribution of hubcap itself can be estimated, and it is known to control the orientation of the hubcap with respect to the wheel. As illustrated in FIG. 14, a hubcap 200 may be provided with projecting pins 202 on a flange 204 which pins are received in openings 206 on a wheel flange 208 to ensure that the hubcap 200 is mounted in a desired angular relationship with the wheel 210. However, it has been found that the openings 206 in the wheel flange can concentrate stress in an undesirable manner, and it would be beneficial to eliminate such openings.
Moreover, the clamp (not illustrated in FIG. 14) used to attach the hubcap to the wheel does not have a symmetric mass distribution. Instead, the closure portion of the clamp has more mass than other portions of the clamp. Installing such a clamp on a wheel therefore reduces the balance of the wheel. And, because the clamp can be installed with the closure mechanism in any orientation, the effect of the clamp on the balance of a wheel is difficult to predict.
It is generally desirable to reduce the weight of aircraft components. It would therefore be desirable to reduce the number of weights required to balance an aircraft wheel and to reduce the imbalance imparted to an aircraft wheel by an asymmetrical hubcap clamp.